1. Field of the Invention
The present invention relates generally to optical fiber devices and methods, and in particular to improved techniques for analyzing crosstalk in multicore fibers.
2. Background Art
Multicore fibers are becoming an increasingly important technology. Multicore fibers have been researched for many years, but are currently seeing a resurgence of interest as one of few remaining ways to significantly increase the capacity per fiber. In particular, multicore fibers potentially offer large improvements in cost and compactness for some systems, including some short-length interconnects where fiber congestion is a problem. At the same time, demand is quickly driving core telecommunications links towards fundamental limits of capacity per fiber, even assuming advanced modulation formats.
While it is clear that a multicore fiber can carry a lot of capacity, this technology will only be able to compete broadly with standard multiple fiber solutions if a number of technical hurdles are overcome. When comparing the cost and performance of a multicore to a multiple fiber solution, crosstalk is an obvious potential disadvantage of multicore. Crosstalk places significant constraints on the density of cores in a multicore fiber. Thus, maintaining low levels of crosstalk may be crucial to achieving high density.
Low-crosstalk multicore fiber designs are being actively researched. Multicore fibers can be engineered to have low crosstalk, but are typically subject to tradeoffs with other important parameters: effective area, density of cores, and cutoff. Nonlinearity and density of cores impose significant limits on the ultimate capacity scaling, and also determine the amount of signal processing, and thus electronic power consumption, that is necessary to recover transmitted information. Thus, strategies for achieving low crosstalk with low nonlinearity are thus of great interest.
An accurate crosstalk model is an important component in the development of a low-crosstalk multicore transmission link. Although models of crosstalk have been developed, these models have been proven to be unreliable. In particular, there have been large, qualitative disagreements between modeled crosstalk behavior and measurements taken from actual fibers.
Thus, there remains a need for improved multicore fiber designs that better address crosstalk between the cores as well as improved models and techniques for estimating crosstalk in such fibers.